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Diffstat (limited to 'fs/namespace.c')
-rw-r--r--fs/namespace.c99
1 files changed, 47 insertions, 52 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 9c0e0af64..88ec0984a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2188,13 +2188,7 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
}
if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
!(mnt_flags & MNT_NODEV)) {
- /* Was the nodev implicitly added in mount? */
- if ((mnt->mnt_ns->user_ns != &init_user_ns) &&
- !(sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT)) {
- mnt_flags |= MNT_NODEV;
- } else {
- return -EPERM;
- }
+ return -EPERM;
}
if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) &&
!(mnt_flags & MNT_NOSUID)) {
@@ -2378,7 +2372,7 @@ unlock:
return err;
}
-static bool fs_fully_visible(struct file_system_type *fs_type, int *new_mnt_flags);
+static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags);
/*
* create a new mount for userspace and request it to be added into the
@@ -2388,7 +2382,6 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
int mnt_flags, const char *name, void *data)
{
struct file_system_type *type;
- struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
struct vfsmount *mnt;
int err;
@@ -2399,26 +2392,6 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
if (!type)
return -ENODEV;
- if (user_ns != &init_user_ns) {
- if (!(type->fs_flags & FS_USERNS_MOUNT)) {
- put_filesystem(type);
- return -EPERM;
- }
- /* Only in special cases allow devices from mounts
- * created outside the initial user namespace.
- */
- if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
- flags |= MS_NODEV;
- mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
- }
- if (type->fs_flags & FS_USERNS_VISIBLE) {
- if (!fs_fully_visible(type, &mnt_flags)) {
- put_filesystem(type);
- return -EPERM;
- }
- }
- }
-
mnt = vfs_kern_mount(type, flags, name, data);
if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
!mnt->mnt_sb->s_subtype)
@@ -2428,6 +2401,11 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
if (IS_ERR(mnt))
return PTR_ERR(mnt);
+ if (mount_too_revealing(mnt, &mnt_flags)) {
+ mntput(mnt);
+ return -EPERM;
+ }
+
err = do_add_mount(real_mount(mnt), path, mnt_flags);
if (err)
mntput(mnt);
@@ -3219,22 +3197,19 @@ bool current_chrooted(void)
return chrooted;
}
-static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
+static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new,
+ int *new_mnt_flags)
{
- struct mnt_namespace *ns = current->nsproxy->mnt_ns;
int new_flags = *new_mnt_flags;
struct mount *mnt;
bool visible = false;
- if (unlikely(!ns))
- return false;
-
down_read(&namespace_sem);
list_for_each_entry(mnt, &ns->list, mnt_list) {
struct mount *child;
int mnt_flags;
- if (mnt->mnt.mnt_sb->s_type != type)
+ if (mnt->mnt.mnt_sb->s_type != new->mnt_sb->s_type)
continue;
/* This mount is not fully visible if it's root directory
@@ -3243,12 +3218,8 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
continue;
- /* Read the mount flags and filter out flags that
- * may safely be ignored.
- */
+ /* A local view of the mount flags */
mnt_flags = mnt->mnt.mnt_flags;
- if (mnt->mnt.mnt_sb->s_iflags & SB_I_NOEXEC)
- mnt_flags &= ~(MNT_LOCK_NOSUID | MNT_LOCK_NOEXEC);
/* Don't miss readonly hidden in the superblock flags */
if (mnt->mnt.mnt_sb->s_flags & MS_RDONLY)
@@ -3260,15 +3231,6 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
if ((mnt_flags & MNT_LOCK_READONLY) &&
!(new_flags & MNT_READONLY))
continue;
- if ((mnt_flags & MNT_LOCK_NODEV) &&
- !(new_flags & MNT_NODEV))
- continue;
- if ((mnt_flags & MNT_LOCK_NOSUID) &&
- !(new_flags & MNT_NOSUID))
- continue;
- if ((mnt_flags & MNT_LOCK_NOEXEC) &&
- !(new_flags & MNT_NOEXEC))
- continue;
if ((mnt_flags & MNT_LOCK_ATIME) &&
((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
continue;
@@ -3288,9 +3250,6 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
}
/* Preserve the locked attributes */
*new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
- MNT_LOCK_NODEV | \
- MNT_LOCK_NOSUID | \
- MNT_LOCK_NOEXEC | \
MNT_LOCK_ATIME);
visible = true;
goto found;
@@ -3301,6 +3260,42 @@ found:
return visible;
}
+static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags)
+{
+ const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
+ struct mnt_namespace *ns = current->nsproxy->mnt_ns;
+ unsigned long s_iflags;
+
+ if (ns->user_ns == &init_user_ns)
+ return false;
+
+ /* Can this filesystem be too revealing? */
+ s_iflags = mnt->mnt_sb->s_iflags;
+ if (!(s_iflags & SB_I_USERNS_VISIBLE))
+ return false;
+
+ if ((s_iflags & required_iflags) != required_iflags) {
+ WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
+ required_iflags);
+ return true;
+ }
+
+ return !mnt_already_visible(ns, mnt, new_mnt_flags);
+}
+
+bool mnt_may_suid(struct vfsmount *mnt)
+{
+ /*
+ * Foreign mounts (accessed via fchdir or through /proc
+ * symlinks) are always treated as if they are nosuid. This
+ * prevents namespaces from trusting potentially unsafe
+ * suid/sgid bits, file caps, or security labels that originate
+ * in other namespaces.
+ */
+ return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
+ current_in_userns(mnt->mnt_sb->s_user_ns);
+}
+
static struct ns_common *mntns_get(struct task_struct *task)
{
struct ns_common *ns = NULL;
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-17 20:11:29 +0000